Session 5 – NPSH Made Simple (well, Simpler Anyway!)

Specialist for Pumping Technology

Session 5 – NPSH Made Simple (well, Simpler

Anyway!)

Simon Smith July 2021

Presenter

Presentation Notes

Pre -commencement Oscillate slides 1 & 2

Simon graduated with an honours degree in Chemical Engineering from the University of Surrey in 1978 and began a long career in the engineered pump industry spanning 40 years (so far!) with Peerless Pump, BW/IP International / Flowserve, SPP Pumps, Ruhrpumpen and Ebara Cryodynamics.Over his long career he has filled various roles as Applications Engineer / Manager, Project Manager, Key Account Specialist, Vertical Pump Product Specialist, International Sales Engineer / Manager / Director and he has considerable experience in Training & Mentoring young engineers.

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Presenter Profile – Simon Smith

Presenter

Presentation Notes

Commence on Slide 2 Morning Session Good morning to those of you in Europe & Africa, good afternoon and evening to those of you joining us from Asia, and a very warm welcome to you all. Evening Session Good morning to those of you on the West Coast, good afternoon to those of you joining us from the East Coast , good evening to anyone joining us from Europe or stations further East. Thank you for joining this, the fifth of our regular series of short courses on pumping topics. This one will last about 35-40 minutes allowing us the time for a Q&A session after the presentation Those of you who attended any of the earlier sessions will know that We are deliberately steering away from product presentations and towards educational content, addressing a pumping topic in each one. We believe this is very important in the new world order of many engineers working from home making in-workplace training that much more difficult. Having said that, please forgive me four or five brief slides to remind you who we are and what we do.

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OUR PUMP LINESRuhrpumpen offers a broad range of highly engineered and standard pumping products that meet and exceed the requirements of the most demanding quality specifications and industry standards.

Our pumps can handle head requirements as high as 13,000 ft(4,000 m) and capacities up to 300,000 gpm (68,000 m3/hr). Moreover, our pump designs cover temperatures from cryogenic temperatures of -310 °F (-196 °C) up to 752 °F (400 °C).

Products include: Single Stage Overhung Pumps

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Presenter

Presentation Notes

Overhung – Foot mounted or Centreline, ANSI, ISO, General Purpose or API610 Between Bearings – Axially Split, Radially Split, API compliant Multi-stage – Axially Split Case & Radially Split Double Case (Barrel) Vertical - Single stage, Multi-stage, API & General Purpose, Double Case or Single Case Submersible pumps Positive Displacement Mag Drive Packaged Systems Fire Systems I have added a few slides right at the end of the presentation as an appendix, showing the full range of our products. Scroll. But I don’t plan to spend any time on them in this Presentation, you can take a look at your leisure when you get a copy of this Session That is the end of the commercial, now back to the subject matter!

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Session 5 –“NPSH Made Simple (well, Simpler Anyway!)”

Aimed at Process and Mechanical Engineers and Consultant Engineers specifying pumping equipment as well as Applications & Sales Engineers selecting and quoting them. Develop an understanding of the fundamentals and practical aspects of NPSH – probably the most difficult and misunderstood concept in pumpingWill cover such topics as Cavitation damage, Suction Specific Speed and the “11,000 limitation”, understanding the NPSH Curve

Presenter

Presentation Notes

This seminar is going to look at NPSH. There has been an awful lot written on the subject, some of it really good, and if I whet your appetite sufficiently I have given some links and references at the end of the presentation for your future reading and viewing. The aim of this 30 minute session is to give you a basic understanding of NPSH, what it is and how it affects us. I will also be explaining Suction Specific Speed and particularly why there is a limit of 11,000. We will be holding a Q&A session at the end. Unfortunately the nature of a Zoom format for these seminars makes a fully interactive Q&A impossible with so many attendees. At the last count there were over 150 attendees for this session alone and we had over 200 attendees for all of the previous sessions. So it won’t be fully interactive but we will do the best we can Please use the “Q&A” facility the bottom of your screen to ask any questions or make any comments. I will address those that I can live at the end of the session and the rest we will address by mail in the coming days. We are recording this session and will make it available to all attendees as a You-Tube link as well as by emailing you a PDF version of the slideshow. .

1. NPSHA

2. NPSHR

1. What it is

2. How we measure and test for it

3. Cavitation1. NPSH induced Cavitation

2. Low Flow Recirculation induced Cavitation (suction & discharge)

4. Suction Specific Speed (NSS)1. What it is

2. The 11,000 limitation

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NPSH Made SimpleContents

At any given temperature, all liquids have a definite pressure at which they boil. Every day we witness the fact that a liquid boils at atmospheric pressure when it reaches a sufficiently high temperature. It is important to remember also that a liquid will boil at any temperature if the pressure is reduced sufficiently. While at sea level water boils at 1000C (2120F) at the top of Mount Everest it boils at 680C (1540F)It is the problem of the Process & Applications Engineers to make certain that there is enough pressure on the fluid being fed to the pump so that the liquid does not boil in the suction of the pump.

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NPSHAWhat it is.

Presenter

Presentation Notes

CLICK – Read CLICK – This is what we as pump engineers need to do

NetPositive (means head over and above the vapour pressure)Suction (at the suction flange / centreline of impeller)HeadAvailable“The net positive suction head available is the total suction head in feet (meters) of liquid absolute determined at the suction flange minus the vapour pressure of the liquid in feet (meters) absolute”NPSHA = Suction Pressure (ft or m) – Vapour Pressure (ft or m)

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NPSHADefinition

Presenter

Presentation Notes

Definition Here is what the letters NPSH stands for CLICK Here is the definition of NPSHA (Read) CLICK Put another way (Read)

NPSHA = Ha - Hvpa +/- Hst – Hf

Where:-Ha = the head from the absolute pressure acting on the surface of the liquid

(in an open suction system this will be atmospheric pressure, in a closed system it will be the pressure in the suction vessel acting on the surface of the liquid)

Hvp = the head from vapour pressure (always a negative value)

Hst = Static head above the pump impeller centerline (suction flange)

(this value is negative in the case of a suction lift)

Hf = Friction head in pipework (always a negative value)

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NPSHAArithmetically:-

Presenter

Presentation Notes

Here it is expressed arithmetically (Walk through the slide - Especially closed system & suction lift.)

NetPositive (means head over and above the vapour pressure)Suction (at the suction flange / centreline of impeller)HeadRequired (historically by convention the same as NPSH3)NPSH3 is measured and defined as a 3% reduction of pump TDHNPSH1 is measured and defined as a 1% reduction of pump TDH“NPSHR is the total suction head in feet (meters) of liquid absolute measured at the suction flange / centreline of the impeller that corresponds to a 3% (sometimes 1%) reduction in discharge pressure.”

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NPSHR (or 3 or 1)Definition

Presenter

Presentation Notes

Read CLICK Read definition “NPSHR is the total suction head in feet (meters) of liquid absolute measured at the suction flange / centreline of the impeller that corresponds to a 3% (sometimes 1%) reduction in discharge pressure.”

A pressure drop occurs between the pump suction flange and the minimum pressure point within the pump impeller because of:1- An increase in the velocity between the suction flange and entrance to the impeller vanes.2- Friction & turbulence between the suction flange and the entrance to the impeller vanesIt is impossible to design a centrifugal pump in which there is no pressure drop between the suction flange and the entrance to the impeller vanes. All pump systems must have a positive suction head sufficiently high to overcome this pressure drop within the pump and to keep the fluid from boiling at the pumping temperature.

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NPSHR Why a Pump Requires a Positive Suction Head

Presenter

Presentation Notes

This is a bit wordy I am afraid but it is fundamental to understanding what NPSHR is CLICK On all pumps there is a pressure drop as the flow enters the pump. Caused by CLICK (1) an increase in velocity as you enter the pump (this is where a pump expert will nod sagely and say “Bernoulli’s theorem” and the rest of us will say “What?” So as I am making this simple… Bernoulli says simply that an increase in velocity is associated with a decrease in pressure. CLICK (… Caused by….) (2) Friction & turbulence CLICK Its impossible not to have this pressure drop Pump designers seek to minimize it in their designs CLICK System designers seek to ensure that the pump systems have a positive suction head sufficiently high to overcome this pressure drop within the pump and to keep the fluid from boiling at the pumping temperature.

NPSH3 Required

PRES

SURE

LOCATION WITHIN THE PUMP

NPSH Margin = NPSHA – NPSH3.

NPSHA Available

NPSH Margin

IN T

HE S

UCT

ION

PIP

ING

AT T

HE P

UM

P SU

CTIO

N F

LAN

GE

JUST

EN

TERI

NG

THE

IMPE

LLER

AT T

HE IM

PELL

ER V

ANES

A B C D E

VAPOR PRESSURE AT SUCTION TEMPERATUREAT

PU

MP

DISC

HARG

E FL

ANG

E

GOLDEN RULE:-

Per ASME B73 & HI, the NPSHA must always exceed the NPSH3, by 3Ft (1m) or by 1.2 x (NPSHA/NPSH3).

NPSHRVisually

Presenter

Presentation Notes

Here it is visually and graphically You will see here the pressure profile as flow goes through the pump A- Within the Suction piping. Fluid friction gradually reduces the pressure in the Suction piping as the liquid flows towards the pump. B- At the Pump Suction Flange. At the Pump Suction Flange the liquid begins to accelerate into the tapered pump suction nozzle. Bernoulli’s theory tells us that as a fluid accelerates it reduces in pressure, so a further pressure drop occurs C- Just Entering the Impeller. As the liquid enters the Impeller, the acceleration continues as the area gets slightly smaller at the Impeller eye. So yet another pressure drop occurs within the pump. D- At the Impeller Vanes. As the liquid travels further into the Impeller it enters the passages between the impeller Vanes. These passages between the vanes, reduce the area and so this causes the liquid to accelerate. At position D, due to the acceleration that occurs, the pressure drops still further. This is the lowest pressure area within the pump, so the design of this area is very important. E- At the pump Discharge Flange. The centrifugal force added by the impeller Vanes throws the liquid out of the Impeller & into the casing volute channel and to the pump Discharge flange. It is now generating pressure (head)

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NPSHR Typical Pump Test Loop

Presenter

Presentation Notes

Now we are looking at how we measure and test for NPSHR Typical Pump Test Loop

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NPSHR NPSHR Testing Procedure

Sealed Tank Suction valve- Used for “Throttled

suction” NPSHR testing

Presenter

Presentation Notes

When we are NPSHR testing, we need to reduce the suction pressure to the point at which boiling occurs. This pressure reduction can be achieved in 1 of 2 ways:- By “Suppression testing”, where a Vacuum is pulled on the air-gap at the top of the sealed Test Tank. This is the most accurate NPSHR Tests. So we are going to take 5 or 6 flow rates and while maintaining the flowrate we will reduce the suction pressure (either by pulling a vacuum or by throttling the suction) all the time measuring the discharge pressure until we see a 3% drop in discharge pressure. Then we reset for the next flow rate and repeatBy the “Throttled suction technique”, where suction pressure is reduced by gradually closing the suction valve. This is not the most accurate NPSHR Tests. NOTE:- Both NPSHR testing methods are acceptable to API610 and industry standards.

• The pump is set to the rated speed.

At each flow point (typically 5 or 6 flows), while the Suction Pressure is reduced, the Discharge Valve is opened slightly to maintain the constant set Flowrate.

At each NPSHR Test point, Flow, Head, Suction pressure & Water Temperature readings are taken at progressively lower and lower Suction pressures. Whether the reduction in Suction pressure is due to a Vacuum Suppression Test or a Throttled Suction valve Test.

At some point, as the Suction Pressure is reduced more and more, the Pump Differential Head will get closer to a 3% Head reduction. So now the Suction Pressure Reduction values are taken closer together.

After the Head drop has reached 3% at every Flowrate, the NPSH3 test is completed.

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NPSHR NPSHR Testing Procedure

Presenter

Presentation Notes

A summary of what I just said

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NPSHR NPSH Test Curve

0

5

10

15

20

25

0 100 200 300 400 500

NPS

H3 (F

t)

Flow USGPM

NPSH Curve

Presenter

Presentation Notes

6 flow rates First one 126gpm Gradually reduce the suction head (the NPSHA) and measure the discharge head Here are the points and here is where we get a sudden fall off in discharge pressure Repeat for the next flow, and the next. Next we determine what suction pressure corresponds to a 3% drop for each flow and plot your NPSH Curve CLICK Here 126gpm corresponded to 10ft NPSHA And so on for all 6 flows

"Suction cavitation occurs when NPSHa (available) is less than NPSHr (required)."This is completely wrong and a misunderstanding of the physics involved in a centrifugal pump. Here is why:

• Consider that NPSHr is normally determined where the pump head has already degraded by 3%. By that point there is already extensively developed cavitation in the impeller.

• Simply raising NPSHa slightly above NPSHr does not result in that cavitation magically disappearing. You need to go to much higher suction pressures to completely eliminatecavitation.

• For an "average" centrifugal pump, to completely eliminate cavitation, the NPSHa would need to be >500% of the NPSHr (specifically the NPSHi point shown on the example below).

Source – Simon Bradshaw - Director Engineering, Pumps Americas at CIRCOR

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NPSHRCommon Misconception

Presenter

Presentation Notes

Let me clear up a big misconception CLICK It is NOT sufficient for NPSHA to equal NPSH3 CLICK At the NPSH3 point you already have boiling and cavitation going on CLICK To avoid any NPSH cavitation damage you need a to go to a much higher suction pressure CLICK

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NPSHROnset of Cavitation

Source – Simon Bradshaw - Director Engineering, Pumps Americas at CIRCOR

All pumps operate with suction cavitation. The only question is whether it is damaging cavitation.

Presenter

Presentation Notes

Talk through the points CLICK Here is the point All pumps operate with suction cavitation. The only question is whether it is damaging cavitation.

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As the suction head value gets closer to the NPSH3 value, vapour bubbles form on the underside of the inlet vanes of the impeller.

The closer you get to the NPSH3 value the more bubbles will form and over a larger area of vane.

As these bubbles are swept into higher pressure areas they collapse with a shock

Cavitation

Presenter

Presentation Notes

So in the last few slides I have started to talk about cavitation. Here is what we are talking about. Talk through the slide

When a Cavitation vapour bubble collapses, the instantaneous pressure of this small, high energy shock-wave is many thousands of PSI over an extremely small area.

There are two progressive shock waves that impact the metal surface against the bubbles:-

The initial MICRO-JET formed when the top surface of the bubble starts to collapse.

Immediately after this micro-jet, the whole surface of the bubble then collapses & returns to liquid form.

Shock waves are formed by collisions among the surrounding liquid molecules, that rush in to fill the void caused by the collapsing bubble.

Research has shown that the life span of a Cavitation bubble from formation to collapse, is about two milliseconds (two one-thousands of a second), so this event occurs very rapidly.

The more rapidly the surrounding Liquid collides, the greater is the energy of the damaging shock-wave & micro-jet.

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CavitationThe Cavitation Mechanism

Presenter

Presentation Notes

Again this is a bit wordy I will read it through

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CavitationThe Cavitation Mechanism

This illustration shows the progression of the vapor bubble collapse.

These ultra-high speed Laboratory photos belowshow this progression:- Below is a photo showing the

micro-burst jet, just before the final collapse:-

Presenter

Presentation Notes

Here it is visually

The extent of the damage will depend on several factors: The size of the bubbles formed

The Density of the fluid

Thermodynamic effects (Enthalpy & Latent heat)

These combined effects comprise “Thermal Cavitation Criteria –B” (see next slide)

But simply put:

Cold water forms big bubbles and has a high density, so the damage done when the bubbles collapse is high

Hydrocarbons form small bubbles and have a lower density, so the damage done when the bubbles collapse is much less

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CavitationExtent of the Damage

Presenter

Presentation Notes

All pumps operate with suction cavitation. The only question is whether it is damaging cavitation. So let’s do that CLICK CLICK size, density enthalpy & latent heat CLICK “Thermal cavitation Criteria B” - I can see your eyes glazing over CLICK But this course is “NPSH made simple” so simply and effectively put CLICK Cold water… CLICK Hydrocarbons…

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CavitationExtent of the Damage – in More DetailCOMPARITIVE VALUES OF THE THERMAL CAVITATION CRITERIA-B:-Below we show a list of the various THERMAL CAVITATION CRITERIA-B values for Water which exhibits high cavitation damage, and Butane, a light hydrocarbon, which usually exhibits a much lower cavitation damage rate.

Thermal Cavitation Water Water Water Water Butane

Criteria B 70F 180F 212F 300F 70F

Value of B 253 1.048 0.324 0.0223 0.0202

This shows why one of the worst liquids to produce damaging cavitation erosion is COLD WATER. As this has a very high ratio of vapour to liquid and a high density (relative to hydrocarbons which increases the kinetic energy of the cavitation micro-jet causing the erosion damage.

Presenter

Presentation Notes

Here in a little more detail The higher the value the more damaging So cold water is 12,000 times more damaging than Butane And interestingly hot water is significantly less damaging than cold water. Bearing this in mind and remembering that pumps are tested on cold water – the worst case, there is a strong case for a hydrocarbon correction factor. CLICK

Allowed by HI

Not allowed by API since 6th

edition

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CavitationHydrocarbon Correction Factor

Presenter

Presentation Notes

This is allowed by HI but not by API any longer. Went out in 5th or 6th edition Here is how it used to work This chart is still in the current HI Standards

ANSI / Hydraulic Institute Standard Para 9.6.1 addresses NPSH Margin

API Pumps in hydrocarbon service

NPSH Margin (NPSHA / NPSH3) = 1.1 or 1m (3.3ft)

in the allowable operating range (AOR)

Chemical Process Pumps

with Nss <11,000, NPSH Margin (NPSHA / NPSH3) = 1.1 or 0.6m (2ft)

with Nss >11,000, NPSH Margin (NPSHA / NPSH3) = 1.2 or 1.0m (3.3ft)

in the allowable operating range (AOR).

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CavitationNPSH Suggested Margins

Presenter

Presentation Notes

Suggested Margins CLICK API pumps CLICK Chem Process Pumps

Occurs when pumps operate back on the curve from BEP

When two flow paths within a fluid are moving in opposing directions and in close proximity to each other, vortices form.

These vortices result in low pressure areas (where bubbles form) and high pressureareas (where they collapse).

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Suction & Discharge RecirculationA Different kind of Cavitation

Presenter

Presentation Notes

Now there are two other types of Cavitation you need to know about that are nothing to do with NPSH cavitation Suction & Discharge Recirculation They occur when pumps operate back on the curve from BEP Suction recirculation cavitation is often confused with NPSH cavitation When you operate away from BEP you WILL get recirculation vortices HERE and HERE (Read slide)

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Suction RecirculationA Different kind of Cavitation

Suction Recirculation Cavitation Damage appears on back side (pressure side) of vane

NPSH Cavitation Damage appears on front side (suction side) of vane

Suction Recirculation Cavitation Damage appears on back side (pressure side) of vane. You need a dentist’s mirror to see it under here.

Presenter

Presentation Notes

Suction recirculation damage occurs here on the opposite side of the vane to NPSH damage You need a dentist’s mirror to see it You can see why people confuse the two

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Discharge RecirculationA Different kind of Cavitation

The central core of the Discharge Recirculation Vortex, is such a low pressure that the liquid starts to vapourise& as the bubbles move to the outer area of the vortex, where the pressure is much higher, they Cavitate (implode) against the Impeller Shrouds, and cause the hole damage shown.

Presenter

Presentation Notes

Discharge recirculation will lead to damage on the shrouds of the impeller

The quickest and easiest way to identify the real cause of the noise, loss of performance, reduced power & vibration, is merely to throttle the discharge valve…This will cause the pump flow to reduce, so that one of three events will occur, which allows the true cause to be found:-

Event 1:- If the rumbling & rattling sound reduces, or in fact may be eliminated entirely….

The pump is now running at a lower flow with lower NPSHR requirements. So this event indicates that NPSH Cavitation was the real culprit.

Event 2:- If the rumbling & rattling sound, and the vibration increases…..

This tells us that the pump is moving into a lower flow condition causing the situation to get worse. So this event indicates that Suction and/or Discharge recirculation was the real culprit.

Event 3:- OR- If the result, is that there is no change in the sound or vibration……

This tells us the events are unaffected by flow. So this event indicates that Air or Gas entrainment in the Liquid was the real culprit.

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Cavitation – Which Type Have I Got?

Presenter

Presentation Notes

“Aaaaaaarrrggghhhh” I hear you scream. “Which type have I got? How can I tell in the field?” CLICK Read

THE FOLLOWING MATERIALS ARE PROGRESSIVELY MORE RESISTANT TO EROSION & CAVITATION DAMAGE. STARTING WITH CAST IRON AS THE LEAST RESISTANT:-1. Cast Iron…………… Least Resistant.2. Leaded Bronze.3. Cast Carbon Steel.4. Manganese Bronze.5. Monel.6. Chrome and Stainless Steels:-

CA15 & CA6NM (Martensitic) & CF8M (Austenitic).7. Cast Duplex Stainless Steels.8. Cast Nickel Aluminum Bronze.9. Alloyed Titanium.10. Cast Carburized 12% Chromium Stainless and Chrome Manganese

Austenitic Steels.....................Very Resistant.11. Stellite coating………………..Most Resistant.

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Cavitation DamageHow can I Minimise or Mitigate the Damage?

Presenter

Presentation Notes

When you cannot increase NPSHA sufficiently to solve a cavitation situation you might need to consider selection of materials for the impeller to minimise the impact. Note how cast iron and bronze (the two most common impeller materials for water service pumps) are the least resistant to cavitation damage. Note how CA6NM (12% Chrome steel) is a pretty resistant material, is inexpensive and is commonly supplied by pump manufacturers

You may think of it as a dimensionless number * that describes the NPSH capability of an impellerDefined as:-

NSS = N(RPM) x Q(BEP Full Dia) 0.5 / NPSH(BEP Full Dia) 0.75

NSS(Metric) = NSS(US) x 1.16 (m3/hr, m, rpm) Almost universally expressed in USGPM, Ft, RPM unitsThe higher the number the lower the NPSHR

Most specifications limit the allowable value to 11,000 (US units) or 12,760 (m3/hr, m, rpm)WHY?

* Except that it isn’t actually dimensionless!

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Suction Specific Speed (NSS)Definition

Presenter

Presentation Notes

Finally we come to Suction Specific Speed Here is its definition (work through slide) CLICK Well here is a history lesson for you

In the 1950's to 1980's the impeller design methods available to pump designers were more limited than they are today. Impeller designs from that era were notable for their achievement of good suction performance through the deployment of large impeller inlet diameters. It was not understood until later that the enlarging of the impeller inlet diameter caused impairment of the impeller performance at flow rates lower than the best efficiency point (BEP). This impairment exhibited itself as significantly increased vibration, Suction Recirculation, and in some extreme cases an unstable NPSHr characteristic.

Warren Fraser – “Flow Recirculation in Centrifugal Pumps” (1981)https://oaktrust.library.tamu.edu/handle/1969.1/163728

In 1981 Warren Fraser published a paper which brought the consequences of relying on large impeller inlet diameters into focus. Pump users had already become increasingly concerned that while such designs minimized plant 1st cost, it was at the price of reliability and overall life cycle cost.

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Suction Specific Speed (NSS)The 11,000 Limit

https://oaktrust.library.tamu.edu/handle/1969.1/163728

Jerry Hallam – “Centrifugal Pumps: Which Suction Specific Speeds are Acceptable?”, Hydrocarbon Processing, April 1982

In 1982 Jerry Hallam published the results of a large scale reliability study of 480 pumps over a 5 year period at the Amoco Texas City refinery. He found that the reliability of a pump was meaningfully related to its suction specific speed (Nss). Specifically pumps with a Nss > 11,000 (S > 12760) failed twice as often compared to lower suction specific speed pumps.

Hallam concluded: "This study indicates that caution should be exercised when purchasing hydrocarbon or small water pumps with a Nss greater than 11,000 unless operation is closely controlled near BEP."

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Lobanoff & Ross, “Centrifugal Pumps: Design & Application 2nd Edition Fig 8-7”

Lobanoff & Ross carried out testing in 1985 which supported this limitation based on the then current state of impeller design.

They tested a range of impellers with differing suction specific speeds from Nss = 7000 to Nss = 20,000. For each impeller the flow was varied until the pump vibration level exceeded the API 610 allowable level of 0.3 inches/sec (7.6 mm/s) peak.

The testing showed a strong correlation of Nss & vibration.

The limit of 11,000 was widely adopted as a hard limit in the oil and gas industry and it is still rare to see a specification that does not invoke it.

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Impeller design has improved by leaps and bounds since the 1980s and many authors have published papers to this effect.Central to their claim was the premise that modern impeller design techniques allowed the attainment of higher suction specific speeds without relying solely on enlargement of the impeller eye.

Bradshaw, Simon; Cowan, David; Liebner, Thomas (2013). “Influence Of Impeller Suction Specific Speed On Vibration Performance.”

https://oaktrust.library.tamu.edu/handle/1969.1/162554In 2013 Bradshaw, Cowan & Liebner of ITT Goulds repeated the Lobanoff & Ross study from 1985 using modern impeller designs and pump construction standards. It is a very interesting read and I would recommend it to you all. I provide a link at the end of this presentation.It would certainly suggest a limit of 13,000 rather than 11,000 and probably as high as 14,776.

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1- Simon Bradshaw - Director Engineering, Pumps Americas at CIRCOR, formerly Sulzer Pumps & ITT Goulds Pumps

“No You Can’t Prevent Cavitation” https://www.linkedin.com/pulse/you-cant-prevent-cavitation-simon-bradshaw/?trackingId=T9h7yxZWQFmQiQJ3IISlPA%3D%3D

2- Ian James – Engineering Manager variously at David Brown Bingham, Dresser Rand, HMD Pumps, RuhRPumpen, Best Pump Works, AMEC, and DXP & Pumpworks.

3- Warren Fraser – “Flow Recirculation in Centrifugal Pumps” (1981)


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Sources & References

Presenter

Presentation Notes

I have borrowed from several sources in preparing this Short Course Particularly from Simon Bradshaw & from Ian James so credit where credit is due. I hope I have whetted your appetite and that you want to know more on the subject. So here are some links and references for you. Within these Simon Bradshaw links you will find links to films of actual cavitation which is particularly interesting.

https://www.linkedin.com/pulse/you-cant-prevent-cavitation-simon-bradshaw/?trackingId=T9h7yxZWQFmQiQJ3IISlPA%3D%3D


4- Jerry Hallam – “Centrifugal Pumps: Which Suction Specific Speeds are Acceptable?”, Hydrocarbon Processing, April 1982

5- Lobanoff & Ross, “Centrifugal Pumps: Design & Application 2nd Edition Fig 8-7”

6- Bradshaw, Simon; Cowan, David; Liebner, Thomas (2013). “Influence Of Impeller Suction Specific Speed On Vibration Performance.”


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Sources & References


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Coming Attractions

There will be a break in these Short Courses during the summer holiday period of July and early August. We will recommence at the end of August.

“Mechanical Seals & Seal Systems”Thur 26th August – 08.00 (UK BST) (Eastern Hemisphere) & 17.00 (UK BST) (Western Hemisphere)

Aimed at Process and Mechanical Engineers and Consultant Engineers specifying pumping equipment as well as Applications & Sales Engineers selecting and quoting them. Develop an understanding of the fundamentals of sealing technology, the types of seals available and their associated sealing support systems (piping plans).

Future subjects in preparation include: Double Case Pumps (Barrel Pumps – BB5) Fire Pump Systems & Packages

Presenter

Presentation Notes

We are taking a break from these Short Courses during the holiday period of July and August and will resume at the end of August. 26th August – that’s 8 weeks today Again two sessions, one for the Easten Hemisphere and one for the Western Hemisphere. The invitation will be published nearer the time. Put it in your diary Stop sharing I am leaving this meeting open for a little while to allow you to post in the Q&A box and I will endeavour to answer those that only need a short answer here and now. Those that need a fuller answer will be answered within a few days. Anything you think of later – email to [email protected] Our marketing team are standing by to direct your questions or suggestions to the best person to answer them and they will be sending you the You Tube recording and PDF of the Presentation If you need a Certificate of Completion for this Short Course – again [email protected] Now – on with the Q&A Thank-you again for attending today. I enjoyed preparing and presenting it. I hope you found it useful. See you on the 1st July (that’s 2 weeks today) for the next Short Course

www.ruhrpumpen.com [email protected]

Specialist for Pumping Technology

Presenter

Presentation Notes

That is where I am leaving this session for today Pause Sharing We have covered the main range of pumps used in the Oil and Gas industries I have not tried to cover Chemicals, Water, General Industrial or Fire. There is a limit to the useful information I can impart in a 30 minute session. I apologise that there were an awful lot of detail slides here. As I said at the beginning I don’t expect you to take them all in. I am not going to hold a pop quiz! I would suggest you print the curves off, laminate them and put them in your top drawer for easy access for the next time you are speccing or selecting a pump. Resume Share

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OVERHUNG PUMPSCATEGORY RP MODEL DESIGN STANDARD

Sealless Magnetic Drive Pumps

CRP-M / CRP-M-CC ISO 2858 & 15783 HI design (OH11)

SCE-M API 685

Foot Mounted OH1 and General

End SuctionPumps

IPP HI design (OH1)

CPP / CPP-L HI design (OH1)ANSI B73.1

CPO / CPO-L HI design (OH1)ANSI B73.1

CRP HI design (OH1)ISO 2858 & 5199

GSD HI design (OH0)

SHD / ESK / SK / SKO SKV / ST / STV HI design (OH1)

SWP HI design (OH3A)

Centerline Mounted SCE API 610 (OH2)

Vertical In-Line Pumps

SPI API 610 (OH3)

IVP / IVP-CC HI design (OH4 / OH5)

IIL HI design (OH5) Dimensionally compliant with ANSI B73.2

SPN API 610 (OH5)

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BETWEEN BEARING PUMPSCATEGORY RP MODEL DESIGN

STANDARD

1 and 2 stage

Axially split

HSC / HSD / HSLHSR / ZW HI design (BB1)

HSM HI design (BB3)

ZM / ZMSZLM / ZME API design (BB1)

Radially splitHVN / J API design (BB2)

RON / RON-D API design (BB2)

Multi-stage

Axially splitSM / SM-I API design (BB3)

JTN API design (BB3)

Radially split single casing GP API design (BB4)

Radially splitdouble casing A LINE API design (BB5)

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VERTICAL PUMPSCATEGORY RP MODEL DESIGN

STANDARD

Singlecasing

Diffuser

VTP HI & API 610 (VS1)

VCT HI & API 610 (VS1)

HQ HI & API 610 (VS1)

VLT HI & API 610 (VS1)

Volute DSV / DX HI & API 610 (VS2)

Discharge throughcolumn – Axial flow VAF HI & API 610 (VS3)

Separate discharge line VSP / VSP-Chem HI & API 610 (VS4)

Doublecasing

Diffuser VLT / VMT HI & API 610 (VS6)

Volute DSV / DX HI & API 610 (VS7)

Submersible pumpsSMF HI design (OH8A)

VLT-Sub / VTP-Sub HI design (VS0)

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SPECIAL SERVICE PUMPSCATEGORY RP MODEL DESIGN

STANDARD

Pitot tube pumps COMBITUBE HI design

Reciprocating pumps RDP API 674ISO 13710

Vertical turbine generator VTG HI design (VS6)

Barge LS BARGE HI design

Floating dock pumpsZVZ HI design

LVZ HI design

Cryogenic pumps

SVNV -

VTG Cryogenic -

VLT CryogenicVLTV -

Pre-packaged firepump systems

Fire systems incorporate pumps, drivers, control systems and pipework in a single container. They can be skid mounted, withor without enclosure and supplied with electric motor ordiesel engine.

NFPA-20-850UL and FM approvedcomponents

www.ruhrpumpen.com

Session 5 – NPSH Made Simple (well, Simpler Anyway!)

Documents

Transcript of Session 5 – NPSH Made Simple (well, Simpler Anyway!)